A comparative study of nanosized iron oxide particles; magnetite (Fe3O4), maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3), using ferromagnetic resonance

We investigated intra/inter particle interactions in single domain size magnetite (Fe3O4), maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3) iron oxide particles. The magnetic analyses were done using vibrating sample magnetometer and magnetic resonance measurements that were taken from 5 to 300 K and from 120 to 300 K, respectively. The magnetic resonance analyses were done for the iron oxides, frozen under 5000 G fields in glycerol matrix. By changing the temperature, a change in resonance field lines was observed at each Fe3O4, gamma-Fe2O3 and alpha-Fe2O3 nanoparticles. However, the fits in resonant lines showed that Lande g values (spectroscopic splitting factor) stayed stable with temperature decrease. The thermal sensitivities that were determined from Lande g factors, revealed three dominant interactions on resonant lines namely; the exchange coupling in between Fe2+, Fe3+ and O (g(1) = 3.01 +/- 0.08), Fe3+ centers (1.88 +/- 0.03 <= g(2) <= 2.02 +/- 0.03, depending on iron oxide states) and flip flop of O ions in between ionic states of Fe2+-O (1) and Fe3+-O (2) (2.35 +/- 0.06 <= g(3) <= 2.44 +/- 0.06, depending on iron oxide states). (C) 2012 Elsevier B.V. All rights reserved